Firearms such as rifles are popular amongst hunters, gun enthusiasts, sharpshooters, military and police personnel, and the like. For example, AK pattern rifles, including the AK-47, AKM, AK-74, and AK-100 rifles are widely appreciated for their substantial reliability, relatively low production costs, and ease of use. However, many firearms, including AK pattern rifles, possess both favorable and unfavorable features.
For example, AK pattern rifles are renowned for consistent performance under a variety of environmental conditions. Additionally, the firing mechanism of an AK pattern rifle is readily accessible within the rifle receiver, making it easy to repair and replace component parts of the firing mechanism. Yet, many users find the typical stock design of an AK pattern rifle to be undesirable. The typical AK-pattern stock is typically milled from a single piece of wood or plastic and assumes downward-sloping trapezoidal shape from the receiver toward the user. As a result, the stock is heavy, is not easily customized, and is therefore not ideal for users of varying builds and shooting styles. Moreover, the downward slope of the AK pattern stock results in a nonlinear recoil path; that is, recoil action from firing is not transmitted in a straight line from the barrel back to the user's shoulder or other body part. This results in a recognizable feeling when the shooter absorbs and manages the recoil of an AK pattern rifle.
Other types of rifle stocks enjoy advantages over the AK pattern stock. For example, the stock of an AR-15 semiautomatic rifle is a lightweight, customizable, and ergonomically favorable stock that is amenable to use by users of varying builds and shooting styles. The AR-15 stock typically possesses a relatively low-profile, minimalist design, making the typical AR-15 stock lighter than the typical AK pattern stock. Additionally, the AR-15 stock attaches generally in line with the barrel, creating a straight recoil path from the barrel to the user's shoulder in the standard firing position. Moreover, the length of the AR-15 stock may be adjusted by pulling, thereby permitting a customized fit for a given user's body type and preferred shooting style. Thus, the stock may sit snugly against the lower receiver for use by a shooter with shorter arms or one who prefers tight control over the rifle, or may be extended away from the receiver for use by a shooter with longer arms or one who is otherwise more comfortable with a longer rifle configuration.
The differences between the typical AK pattern and AR-15 stocks are reflected in the connection mechanism between the stock and the receiver. For example, the AR-15 stock connects to the AR-15 lower receiver by means of a threaded, generally cylindrical buffer extension tube housed within a recess formed in the stock opposite the butt end. The buffer tube protrudes from the recess and mates with a round, threaded aperture formed in an upwardly projecting portion of the lower receiver. The upwardly projecting portion is disposed in line with the barrel, above the main body of the lower receiver and the firing assembly components housed therein.
The AK pattern stock, on the other hand, defines a roughly rectangular block opposite the butt end and a recess along a top surface of the stock. A first end of the receiver defines a downwardly-angled face with a rectangular opening for receiving the block. A protrusion located above the rectangular opening protrudes toward the stock at a slight downward angle. When the block is inserted into the rectangular opening, the recess receives the protrusion. The protrusion includes an aperture through which a screw or pin may be extended, with an extending portion of the screw or pin being received by the recess to secure the stock to the receiver. Some variations of the AK pattern stock and receiver include a second protrusion below the rectangular opening at the stock first end and a corresponding second recess along the bottom surface of the stock.
Other differences exist between the AR-15 and AK pattern receivers. For example, unlike the AR-15 lower receiver, the AK-47 receiver defines an aperture for receiving the rifle barrel opposite the stock connection. Moreover, the AK pattern receiver houses all of the internal mechanisms, including the firing bolt, bolt carrier, piston, carrier spring, hammer assembly, trigger guard rivets, firing pin assembly, and disconnector assembly, in a single, relatively accessible space. This design allows for straightforward removal and replacement of the various components. The internal mechanisms of the AR-15, on the other hand, are split between the lower receiver, which couples to the stock, and an upper receiver, which receives the barrel. The internal space of the AR-15 lower receiver is somewhat tighter and more difficult to easily navigate than that of the AK pattern receiver.
Some attempts have been made to combine the favorable characteristics of various rifle types, including the AR-15 and AK pattern rifles, to create a firearm that enjoys multiple advantages over its various substituent firearms. For example, adapters have been created that interface with a receiver from a first firearm type and a stock from a second firearm type at an opposing surface. One example is an adapter configured to mate an AK pattern receiver with an AR-15 stock.
However, this approach suffers numerous shortcomings. For example, many such adapters are configured to replace the downwardly-angled first end of the AK pattern receiver to provide a vertical first end that facilitates receiving the AR-15 stock. This arrangement prevents the shooter from experiencing the recognizable feeling when absorbing and managing the recoil of an AK pattern rifle
Further, such replacement adapters are relatively small, easily lost, may break or warp, and can be costly to replace. Importantly, the introduction of an adapter between the receiver and the stock may create inconsistencies if the fit between the three pieces is less than perfect, or if the adapter wears over time and use. Such inconsistencies can affect the accuracy, recoil action, and integrity of the firearm, leading to unreliable and dangerous performance.